1. Field of the Invention
The present invention is related to data recorders and printers and, more particularly, is directed towards a data recorder for recording and printing both digital and analog data simultaneously on a common strip chart.
2. Description of the Prior Art
Airborne detection systems utilize many different types of special sensing equipment for monitoring, detecting, and recording various data.
Typical of such airborne sensors and detecting equipment is a unit known as a condensation nuclei counter which basically provides a particle monitoring function for detecting, for example, atmospheric pollution or personnel activity on the ground. Such condensation nuclei counters, whose principles of operation are well-known and therefore need not be set forth herein in detail, generally provide an output analog voltage in direct proportion to the sensed activity level.
When equipment such as the above-described condensation nuclei counters are utilized in an airborne detection unit, it becomes important to be able to correlate the analog output voltage from the counters with the position of the aircraft at any given time. In this manner, maximum and minimum analog readings output by the sensors may be pinpointed to precise locations on the ground. This becomes particularly important in connection with personnel detection sensors since, in warfare, effective retaliatory action must be swift and accurate.
Such position information is digitally output from the aircraft's navigation computer, which may, for example, comprise a LORAN-C navigation unit, and, as noted above, must be time-coordinated with the analog readings from the condensation nuclei counters.
The technique previously utilized to time correlate such data was primarily manual in nature and therefore lead to much error and was generally quite time consuming. It consisted simply of the operator of the equipment visually noting the occurrence of, for example, a maximum voltage reading on a meter connected to the condensation nuclei counters' output, and then manually recording from another remote output the navigation unit digital output reading at that particular moment in time. These two pieces of data had to then be further manually reduced in order to transform the navigator computer output into a meaningful reading for retaliatory strikes. The importance of swift and accurate analog and digital data correlation and reduction is magnified when considered in connection with fast-changing warfare requirements and the generally swift mobility of the enemy.
A non-manual time-coordination alternative reduces to a requirement for a recorder which enables the simultaneous real time recording of both analog and digital data in the same unit. However, it was found that such a recorder was not available commercially.
A not insignificant factor taken into account in the search for a suitable recording device was the extremely limited space within existing surveillance aircraft such as helicopters. A suitable recorder, therefore, had to be designed so as to occupy a minimum amount of space so as to be compatible with and easily installed within existing surveillance aircraft.